Channel Quality Determination of a Wireless Communication Channel Based on Received Data

ABSTRACT

The invention refers to a method of determining a channel quality of a communication channel between a wireless transmitter and a wireless receiver, comprising receiving a transport block with one or a plurality of a modulation symbols (y 1 , . . . , y m ) comprising a plurality of encoded information bits (x 1 , . . . , x n ), de-mapping the modulation symbols to a plurality of soft values (LLR 1 , . . . , LLR n ), calculating a mutual information—MI—measure (MI) as a function of the plurality of soft values (LLR 1 , . . . , LLR n ), wherein the MI measure is indicative of a mutual dependence between the information bits (x 1 , . . . , x n ) and the corresponding soft values of said transport block, and determining a channel quality indication value (CQI-Index) as a function of the MI measure (MI). The invention further refers to a program and to a wireless receiver for performing the method.

TECHNICAL FIELD

The present invention relates to channel characteristics determination,and specifically to channel quality estimation of wireless communicationchannels within a mobile communications networks.

BACKGROUND

In wireless communication systems, a variation of the signal strength ofa communication channel may occur e.g. due to environmental variationscaused by a movement of a wireless terminal (due to multipathpropagation variations, or to shadowing from obstacles); such channel isalso being referred to as a fading channel. The channel quality of afading channel might vary over time, frequency and space. If the channelquality is accurately estimated at a receiver's side, e.g. one of theterminals, it can be exploited by a transmitter, e.g. a base station ofthe mobile communications network to optimize the data transmission. Inparticular, in frequency division duplexing (FDD) systems includingsystems based on orthogonal frequency-division multiplexing OFDM, theterminals might estimate the channel quality to be fed back to thetransmitter within a reasonably short feedback time. If the transmitterhas the knowledge of downlink channel quality, the average throughput(and thus spectral efficiency) at the receiver side can be maximizedwhile maintaining certain Quality of Service (QoS) parameters, e.g. aguaranteed bit-error rate.

A general problem for channel quality estimation is to estimate a blockerror rate (BLER) for a data packet transmitted over a communicationchannel using a plurality of sub channels, especially in OFDM systems,wherein a communication channel is divided into a multiple (narrow-band)sub-carriers, which allows orthogonal modulated streams of data to betransmitted in parallel on the sub carriers, assuming that the currentpropagation channel conditions in a frequency selective fading channelhaving different signal-to-interference-noise-ratios (SINR) persub-carrier.

There are well known CQI estimation methods discussed in literature,e.g. a method called Exponential Effective SNR Mapping (EESM) beingdescribed in a document titled “System-level evaluation of OFDM—furtherconsiderations”, published by 3GPP under the document number TSG-RANWG1, R1-031303, Nov. 17-21, 2003 and a method called Mutual InformationEffective SNR Mapping (MIESM), e.g. being described in the documenttitled “Effective-SNR mapping for modeling frame error rates inmultiple-state channels”, published by 3GPP under the document numberC30-20030429-010, WG RAN1, 2003. Both methods use reference signals,i.e. utilize the estimated channel and noise variance for thecomputation of a channel quality indicator CQI.

If linear receivers (e.g., zero-forcing or minimum mean square error)are employed, the estimated effective channel and noise variance e.g.based on (cell-specific) reference signals might be used for CQIdetermination by post-processing SINRs and calculating an effective SNRvalue based on the post-processed SINRs.

However, CQI estimation based on common (cell-specific) referencesignals might not be accurate enough if it does not precisely accountfor channel estimation errors. Furthermore, if maximum likelihooddetectors are used rather than the linear equalizers, then the CQI can'tbe estimated employing EESM or MIESM methods, as such detectors are notable to deliver SINRs.

SUMMARY

It is an object of the present invention to improve a determination ofchannel quality.

This object is achieved by the independent claims. Advantageousembodiments are described in the dependent claims.

In an embodiment, a channel quality of a communication channel isdetermined at the receiver's side by de-mapping a sequence of receivedmodulation symbols having encoded a plurality of information bits to aplurality of corresponding soft values, calculating an (overall) mutualinformation—MI—measure as a function of the plurality of soft values,wherein the MI measure is indicative of a mutual dependence between theplurality of information bits and the plurality corresponding softvalues, also being referred to as soft bits that represent a reliabilityinformation with respect to a corresponding “hard decision” of whetheran information bit was “1” or “0”. Further a channel qualityindication—CQI—value is determined on the base of the MI measure.

Mutual information is a term generally used in information orprobability theory for a measure of the mutual dependence of two(random) variables. The (overall) mutual information as described aboveshall be indicative of the mutual dependence with respect to theplurality of soft bits. Consequently, the (overall) mutual informationmight be a function of a plurality of particular mutual informationvalues for each one of the plurality of information bits. In anembodiment, the (overall) MI value is an average of the plurality of theparticular MI values. Alternatively, other functions, e.g. a square rootof the sum of squared particular MI values might be chosen to form the(overall) MI value.

The CQI estimation scheme is applicable to communication systems ingeneral where channel quality needs to be evaluated. The above-describedembodiment allows for deriving a channel quality CQI value based onactual data being received. In case of beamforming with dedicatedreference signals (receiver specific beamforming), CQI of the receiverspecific propagation channel would be estimated considering the actualdata transmission.

In contrast to CQI estimation based on user-specific reference signals,the proposed scheme is applicable continuously and thus might yield tomore accurate results, especially if non-linear receivers are employedin the system (it is to be noted that CQI estimation based onuser-specific reference signals can only be evaluated during the actualdata transmission and thus can only be based on a few dedicatedreference symbols).

The MI measure might be determined over all information bits of oneresource or transport block. In this case the MI measure is a valueindicative of a mutual dependency of the whole transport block.

In OFDM based multiple access systems with frequency selective channels,CQI is often used per sub-band (or per bandwidth part) for frequencyselective scheduling of users. Thus, in an embodiment, sub-band specificCQI can be computed by sorting the soft values value according to theirsub-band and processing the sub-band specific soft values individually,if full bandwidth is allocated to the user.

In an embodiment, the soft values are, logarithmic likelihood ratios(i.e. the logarithm dualis of the likelihood ratio), also being referredto as log-likelihood ratios—LLR—, preferably being calculated byde-mapping the received modulation symbols.

In a further embodiment determining the channel quality indication valueis performed by comparing the MI measure with a plurality of certainthresholds and determining a maximum threshold out of the certainthresholds that is below (or equal to) the MI measure, to be chosen aschannel quality indication value and to be reported to the wirelesstransmitter. The thresholds might be chosen to result in a definedtransport block error probability, e.g. a BLER below 10%.

In a further embodiment, each a different set of thresholds are chosenfor different modulation schemes applied for data transmission; e.g. afirst set of thresholds for QPSK, a second set of thresholds for 16QAM,and a third set of thresholds for 64QAM.

In a further embodiment, the MI measure is determined by calculating anaverage over a plurality of particular MI measures that are each beingcalculated as a function of an absolute value of one of the soft values,wherein the soft values are preferably so called log likelihood ratioseach associated to a corresponding one of the information bits beingencoded in the data stream.

In a further embodiment, the thresholds are dependent on at least oneof: the actual modulation and coding scheme, the actual transport blocksize, a particular power setting for the actual transmission, and anassumed power setting for determining the CQI.

In a further embodiment, the communication channel comprises a pluralityof sub channels with potential different sub channel propagationcharacteristics e.g. exhibiting differentsignal-to-interference-noise-ratios (SINR). The sub-channels might berealized as sub-carriers, wherein according to OFDM, a plurality oforthogonal modulated streams of data is transmitted in parallel on thesub carriers.

In a further embodiment, in a multiple input and multipleoutput—MIMO—transmissions environment with a plurality of different codewords, for each code word an individual MI measure, and correspondingCQI values are determined to be fed back to the transmitter (1).

In an embodiment, the proposed metric reuses log-likelihood ratios thatare required for data decoding.

Additional CQI can be introduced to indicate whether transmission withdedicated reference signals is preferred over transmission with commonreference signals.

The present invention also concerns computer programs comprisingportions of software codes in order to implement the method as describedabove when operated by a respective processing unit of a user device anda recipient device. The computer program can be stored on a computerreadable medium. The computer-readable medium can be a permanent orrewritable memory within the user device or the recipient device orlocated externally. The respective computer program can be alsotransferred to the user device or recipient device for example via acable or a wireless link as a sequence of signals.

In the following, detailed embodiments of the present invention shall bedescribed in order to give the skilled person a full and completeunderstanding. However, these embodiments are illustrative and notintended to be limiting.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a principle diagram of a feedback mechanism between areceiver and transmitter of a communication system,

FIG. 2 shows an exemplary block diagram of a receiver comprising aprocessing circuit for determining a CQI-index associated to propertiesof the transmission channel to be fed back to the transmitter,

FIG. 3 shows en embodiment of determining a differential CQI

FIG. 4 shows an exemplary sequence diagram of a sequence being performedin the receiver according to FIG. 2.

DETAILED DESCRIPTION

FIG. 1 shows a principle block diagram for illustrating the concept ofchannel quality feedback within a mobile communications networkaccording to embodiments of the invention. Thereto, FIG. 1 shows atransmitter 1, a communication channel 2 and a receiver 3. By way ofexample, a modulation mapping circuit 11 is shown being comprised by thetransmitter 1, and a modulation de-mapping circuit 31 and a qualityfeedback circuit 32 and a data decoder 33 are shown being comprised bythe receiver 3. By way of example, the modulation mapping circuit 11receives a sequence of information bits x₁, . . . , x_(n) and encodesthem to a sequence of modulation symbols s₁, . . . , s_(m) to betransmitted over the communication channel 2 towards the receiver 3. Themodulation de-mapping circuit 31 receives a sequence of received valuesy₁, . . . , y_(m) that correspond to the modulation symbols s₁, . . . ,s_(m), (but that are generally different due to channel characteristicsand noise being added to the transmitted signals). It is to be notedthat depending on the modulation scheme, a certain number of informationbits are mapped into one modulation symbol, e.g. 2 information bits aremapped into one QPSK symbol, 4 bits are mapped into one 16QAM symbol,and 6 bits are mapped into one 64QAM symbol. A general task of thereceiver 3 is to decode the encoded information bits x₁, . . . , x_(n).

Modern radio access systems, e.g. OFDM systems as described above,employ certain forward error correction schemes, such as convolutionalcodes and convolutional turbo codes. The receiver performance can beimproved by using reliability information, rather than performinghard-decisions. A hard decision and its reliability value are usuallyrepresented by a single so-called soft value also being referred to assoft bits. For instance, soft bits are used as inputs for turbo decodingbased on maximum a posteriori (MAP) and Maximum Likelihood (ML) decodingrule, respectively. Given modulations methods like e.g. Quadrature PhaseShift Keying (QPSK) or a Quadrature Amplitude Modulation (QAM),log-likelihood ratios (LLR) are used as soft bits to be provided to thedecoder. According to such an environment, the modulation de-mappingcircuit 31 de-maps the received values y₁, . . . , y_(m) into a sequenceof de-mapped soft values LLR₁, . . . , LLR_(n). The data decoder 33receives the de-mapped soft values LLR₁, . . . , LLR_(n) to retrieve thesequence of information bits x₁, . . . , x_(n) (i.e. to generate orestimate a sequence of most likely information bits).

As discussed in the introduction, the channel quality of thetransmission channel might vary over time, frequency and space. If thechannel quality is accurately estimated at a receiver's side, it can beexploited by a transmitter to optimize the data transmission.Accordingly, within actual mobile communication systems (e.g. based onLTE), information about the actual channel quality is typically obtainedby the mobile terminals that generate so-called Channel-QualityIndicators (CQI) to be fed back at regular intervals to the basestation. It is to be noted that the CQI does not necessarily explicitlyindicate the channel quality, but rather a data rate supported by thereceiver under the current channel conditions. Accordingly, the termsCQI or CQI index within the scope of this application should beinterpreted broadly as any value based on measured channel conditions tobe fed back from the receiver to the sender in order to set or adjustthe data transmission (e.g. a data rate, a modulation scheme, atransport block size, etc.). Specifically, the CQI might be aninformation that a certain channel condition is met. Such informationmight be coded into a certain number of bits (e.g. 5 bits) representingone CQI index out of a certain number of predetermined indices.

By means of the following FIG. 2 CQI determination within the receiverwill be described in more details. Generally, in an APP (a-posterioriprobability) processor, the soft inputs and the soft outputs area-posteriori probabilities of the encoded information. APP decoding maybe in the log-domain by means of a so-called LogAPP algorithm (alsoknown as LogMAP), which works directly with log-likelihood ratios(LLRs). The outputs of the LogAPP algorithm are a posteriori LLRs of theinfo bits. Further information about LogAPP decoding can be drawn fromthe document titled “Computation of Symbol-Wise Mutual Information inTransmission Systems with LogAPP Decoders and Application to EXITCharts”, of Ingmar Land, Peter A. Hoeher, and Snjezana Gligorevic, Proc.5th Int. ITG Conf. on Source and Channel Coding (SCC),Erlangen-Nuremberg, Germany, January 2004, pp. 195-202.

FIG. 2 shows the modulation de-mapping circuit 31 of FIG. 1, the CQIfeedback circuit being distributed exemplarily into a MutualInformation—MI—determination circuit 32 a and a CQI-Index determinationcircuit 32 b, and a threshold setting circuit 33.

The symbol de-mapping circuit 31 receives the transmitted symbols y₁, .. . , y_(m). Further, this circuit receives a modulation information MDindicating an actual modulation used for the actual transmission, e.g.QPSK, 16QAM, 64QAM, etc. To obtain the log-likelihood ratios LLR(k), themodulation symbols y₁, . . . , y_(m) are de-mapped to so-called softbits. By way of example, the de-mapping circuit 31 is so calledLogMAP/LogAPP demapper rendering log-likelihood ratios LLR(k) as softbits at the output.

The log-likelihood ratios may be further used as input to a data decoderas shown in FIG. 1, e.g. a possible rate-dematching and HARQ combinerfollowed by a Turbo decoder (e.g. working with LogMAP metrics).

The MI determination circuit 32 a determines an overall statisticalinformation or overall mutual information MI from a set of k=N specificmutual information values MI(1), . . . , MI(n) being derived from thecorresponding log-likelihood ratios.

From the absolute value of the k-th log-likelihood ratio that representsa reliability information of the k-th log-likelihood ratio, i.e.|LLR(k)|, the k-th mutual information MI(k) can be extracted:

${{MI}(k)} = {{\frac{1}{1 + {\exp ( {{{LLR}(k)}} )}}{ld}\{ \frac{2}{1 + {\exp ( {{{LLR}(k)}} )}} \}} + {\frac{1}{1 + {\exp ( {- {{{LLR}(k)}}} )}}{ld}\{ \frac{2}{1 + {\exp ( {- {{{LLR}(k)}}} )}} \}}}$

wherein Id shall mean logarithm dualis.

It is to be noted that while the k-th particular mutual informationMI(k) is obtained from the actual data transmitted, it does not dependon the actual value of the information bits.

In order to derive the overall measure statistical information, theoverall MI value is obtained from the MI(k) e.g. by averaging theMI(k)'s over the so-called CQI reference resource, which is the resourcein time and frequency where CQI is to be estimated:

${MI} = {\frac{1}{N}{\sum\limits_{k = 1}^{N}{{MI}(k)}}}$

The MI thus obtained includes characteristics of the physicalpropagation channel as well as potential impairments from imperfectreceiver front end and channel estimation.

The CQI-Index determination circuit 32 b, receives the Mutualinformation MI together with a certain number of sets of thresholds THQPSK, TH 16QAM and TH 64QAM provided by the threshold setting circuit33.

By way of example, the CQI-Index determination circuit 32 b comprises afirst comparison circuit 321 for comparing the MI with a first set ofthresholds TH QPSK, a second comparison circuit 322 for comparing the MIwith a second set of thresholds TH 16QAM, and a third comparison circuit323 for comparing the MI with the third set of thresholds TH 64QAM.Depending on the considered modulation, a corresponding one of thecircuits is activated to determine the CQI-Index.

The CQI index to be reported is by way of example computed by a simplethresholding and maximum operation:

${{CQI\_ Index}( {{MI},{{Threshold}({Idx})}} )} = {\arg \; {\max\limits_{Idx}\{ {Idx} \middle| {{MI} > {{Threshold}({Idx})}} \}}}$

In other words, the CQI index to be reported is the maximum thresholdout of all threshold of the corresponding set that is smaller than theMI. If e.g. QPSK is used, the first comparison circuit 321 is activatedto determine the maximum threshold Idx_(i) out of the thresholds Idx₁, .. . , Idx_(x1) of the first set of thresholds TH QPSK.

It is to be noted that every threshold corresponds to a particularchannel condition and represents a particular CQI index that can bereported. The thresholds might correspond to a minimum MI, wheretransmission is successful with a certain BLER, e.g. 10%, under a givenset of condition for the transmission.

It is further to be noted that The CQI might not explicitly indicate thechannel quality, but rather the data rate supported by the receivergiven the current channel conditions. More specifically, the CQI mightbe a recommended transport-block size (equivalent to a recommended datarate). According to current LTE specifications, the CQI is a 5 bit valueto be fed back from the user equipment (receiver) to the NodeB (sender)at regular intervals.

Averaging the MI(k) values yields an appropriate metrics for CQIestimation, while averaging of the corresponding received SINR over theCQI reference resource would not yield useful metrics for CQI estimationdue to high dynamics of the received SINR across sub-carriers.

The threshold setting circuit 33 might determine the thresholds offlinee.g. by computation through simulations. This circuit might be furtheradjusted online e.g. using long-term statistics e.g. BLER.

The thresholds might depend on the following parameters:

-   -   the modulation scheme MD employed in the actual transmission. As        discussed above a set of different thresholds might be used for        each modulation scheme used in the actual transmission,    -   a modulation and coding scheme defined for the particular CQI        index. It is to be noted that the transport block size might        also change with the chosen modulation and coding scheme,    -   an actual power setting PA and a reference power setting PR for        CQI estimation, or e.g. an offset between the power in the        actual data transmission and the reference power. The reference        power for CQI estimation is defined in some standards, while the        power in the actual transmission (or the power offset between        reference signals and data signals) is usually known in the        receiver. Communications standards, e.g. 3GPP documents, often        prescribe a set of pre-determined transmission powers and,        hence, there is only a discrete set of power offsets that need        to be considered.

In the following, exemplary extensions to sub-band CQI computation andCQI computation per codeword are described:

In OFDM based multiple access systems with frequency selective channels,CQI is often used per sub-band (per bandwidth part) for frequencyselective scheduling of users. Sub-band specific CQI can be computed bysorting the LLR value according to their sub-band and processing thesub-band specific LLR values individually as shown in the previoussection, if full bandwidth is allocated to the user.

In the case of MIMO (multiple inputs and multiple outputs) transmissionswith more than one codeword, the CQI estimation may be performedindividually for each codeword. In particular, the MI values for everycodeword are processed separately as described above to yield twoindividual CQI that are fed back to the transmitter.

For taking a decision between transmission with dedicated referencesignals (also being referred to as beam forming) or common referencesignals, a differential CQI value is proposed that indicates the gainsor losses in data throughput from using dedicated reference signalsversus data throughput from using common reference signals. If thecommunication system allows for switching between transmission withcommon reference signals and transmission with dedicated referencesignals, e.g. as in LTE, this decision can be used to adaptively switchbetween both transmissions.

The CQI for transmission with common reference signals can be obtainedwith well known techniques e.g. employing EESM or MIESM methods asdescribed in the background section. In particular, common referencesignals are transmitted continuously and therefore CQI for commonreference signals can always be evaluated in parallel with CQI fortransmissions with dedicated reference signals. Note that datathroughput (and therefore also CQI) for transmission with dedicatedreference signals might be either higher (due to the improved channelconditions due to user specific beam forming) or lower (due to theincreased overhead from using dedicated reference signals).

In an embodiment, rather than transmitting separate CQI values each fora transmission with common reference signals, and a transmission withdedicated reference signals, only one CQI value is transmitted togetherwith a differential CQI value. Thereto FIG. 3 shows an exemplary blockdiagram with a first CQI determination circuit 41, a second CQIdetermination circuit 42 and a difference circuit 43. The first CQIdetermination circuit 41 determines a first CQI value CQI-Index1 on thebase of the actual received data. Insofar, this circuit might employ thefunctions described under FIG. 3, especially the functions of the MIdetermination circuit 32 a, the CQI Index determination circuit 32 b,and the threshold setting circuit 33. The second CQI determinationcircuit 42 by way of example comprises a CQI estimation circuit 421 anda thresholding circuit 422. The CQI estimation circuit 421 estimates aCQI value based on common reference signals, e.g. employing EESM orMIESM methods as described above. The estimated CQI is fed to thethresholding circuit 422 that selects the maximum threshold below theestimated CQI to determine a second CQI value CQI-Index2. Both the firstCQI value CQI-Index1 and the second CQI value CQI-Index2 are fed to thedifference circuit 43, that determines a differential CQI index by wayof example to be reported together with the second CQI value CQI-Index2based on the common reference signals.

This embodiment allows reducing the feedback data rate. The differentialCQI thereby might include the case that only a 1 bit flag is transmittedwhich indicates whether transmission with dedicated or common referencesignals is preferred.

The described method has particular advantages for the case of beamforming with dedicated (UE specific) reference signals where CQI of thebeam formed propagation channel needs to be calculated based on theactual data transmission.

FIG. 4 shows a flow chart diagram with exemplary summarized steps fordetermining CQI within a receiver as described under FIG. 1:

In a first step 41, log likelihood rations LLR(k) are determined fromreceived modulation symbols.

In a second step 42, a particular mutual information values MI(k) iscalculated for each LLR(k).

In a third step 43, an (overall) mutual information MI is calculated asa summary measure of the particular mutual information values MI(k),e.g. by averaging the particular mutual information values MI(k).

In a fourth step 44, the derived (overall MI) value is compared againsta plurality of thresholds, e.g. each representing a certain channelcondition.

In a fifth step 45, the maximum threshold that is below the derived MIvalue is determined as CQI-Index to be reported to the sender.

1-12. (canceled)
 13. A method of determining a channel quality of acommunication channel between a wireless transmitter and a wirelessreceiver, comprising: receiving a transport block with one or aplurality of a modulation symbols comprising a plurality of encodedinformation bits, de-mapping the modulation symbols to a plurality ofsoft values, calculating a mutual information (MI) measure as a functionof the plurality of soft values, wherein the MI measure is indicative ofa mutual dependence between the information bits and the correspondingsoft values of said transport block, and determining a channel qualityindication value as a function of the MI measure.
 14. The method ofclaim 13, wherein determining the channel quality indication valuecomprises comparing the MI measure with a plurality of certainthresholds and determining a maximum threshold out of the certainthresholds that is below the MI measure, wherein the determined maximumthreshold is to be chosen as the channel quality indication value to bereported to the wireless transmitter.
 15. The method of claim 14,wherein the certain thresholds are chosen to result in a definedtransport block error probability.
 16. The method of claim 13, whereinthe MI measure is determined by calculating an average over a pluralityof particular MI measures that are each calculated as a function of anabsolute value of one of the soft values.
 17. The method of claim 13,wherein the soft values are log likelihood ratios that are eachassociated with a corresponding one of the information bits.
 18. Themethod of claim 13, wherein the communication channel comprises aplurality of sub channels with different sub channel propagationcharacteristics.
 19. The method of claim 18, wherein the sub-channelsare realized as sub-carriers, wherein a plurality of orthogonalmodulated streams of data are transmitted in parallel on the subcarriers, exhibiting different signal-to-interference-noise-ratios(SINR) per sub-carrier, if the communication channel exhibits aselective fading.
 20. The method of claim 13, wherein at least one ofthe certain thresholds is dependent on at least one of: a modulation andcoding scheme, the size of the transport block, a particular powersetting for an actual transmission, and an assumed power setting fordetermining the channel quality indication value.
 21. The method ofclaim 13, wherein multiple input and multiple output (MIMO)transmissions with a plurality of different code words are performed,and wherein the method comprises determining individually for each codeword an individual MI measure, and determining corresponding individualchannel quality indication values to be fed back to the transmitter. 22.The method of claim 13, wherein a further channel quality indicationvalue is determined on the basis of common reference signals, andwherein one of the channel quality indication value and the furtherchannel quality indication value is transmitted together with adifferential channel quality indication value indicative of thedifference of both channel quality indication values.
 23. A wirelessreceiver configured to determine a channel quality of a communicationchannel between a wireless transmitter and the wireless receiver,comprising: a modulation de-mapping circuit configured to receive atransport block with one or a plurality of a modulation symbolscomprising a plurality of encoded information bits and to de-map themodulation symbols to a plurality of soft values, a mutual informationdetermination circuit configured to calculate a mutual information (MI)measure as a function of the plurality of soft values, wherein the MImeasure is indicative of a mutual dependence between the informationbits and the corresponding soft values of said transport block, and aCQI-Index determination circuit configured to determine a channelquality indication value as a function of the MI measure.
 24. Thewireless receiver of claim 23, wherein the CQI-Index determinationcircuit is configured to determine the channel quality indication valueby comparing the MI measure with a plurality of certain thresholds anddetermining a maximum threshold out of the certain thresholds that isbelow the MI measure, wherein the determined maximum threshold is to bechosen as the channel quality indication value to be reported to thewireless transmitter.
 25. The wireless receiver of claim 24, wherein thecertain thresholds are chosen to result in a defined transport blockerror probability.
 26. The wireless receiver of claim 23, wherein the MImeasure is determined by calculating an average over a plurality ofparticular MI measures that are each calculated as a function of anabsolute value of one of the soft values.
 27. The wireless receiver ofclaim 23, wherein the soft values are log likelihood ratios that areeach associated with a corresponding one of the information bits. 28.The wireless receiver of claim 23, wherein the communication channelcomprises a plurality of sub channels with different sub channelpropagation characteristics.
 29. The wireless receiver of claim 28,wherein the sub-channels are realized as sub-carriers, wherein aplurality of orthogonal modulated streams of data are transmitted inparallel on the sub carriers, exhibiting differentsignal-to-interference-noise-ratios (SINR) per sub-carrier, if thecommunication channel exhibits a selective fading.
 30. The wirelessreceiver of claim 23, wherein at least one of the certain thresholds isdependent on at least one of: a modulation and coding scheme, the sizeof the transport block, a particular power setting for an actualtransmission, and an assumed power setting for determining the channelquality indication value.
 31. The wireless receiver of claim 23, whereinmultiple input and multiple output (MIMO) transmissions with a pluralityof different code words are performed, and wherein the mutualinformation determination circuit is configured to determineindividually for each code word an individual MI measure, and whereinthe CQI-Index determination circuit is configured to determinecorresponding individual channel quality indication values to be fedback to the transmitter.
 32. A computer program product stored on acomputer readable medium and comprising computer program code that, whenexecuted by a processing unit of a wireless receiver, causes thewireless receivers to determine a channel quality of a communicationchannel between a wireless transmitter and the wireless receiver,wherein the wireless receiver is configured to receive a transport blockwith one or a plurality of a modulation symbols comprising a pluralityof encoded information bits, and wherein the computer program codecauses the wireless receiver to: de-map the modulation symbols to aplurality of soft values, calculate a mutual information (MI) measure asa function of the plurality of soft values, wherein the MI measure isindicative of a mutual dependence between the information bits and thecorresponding soft values of said transport block, and determine achannel quality indication value as a function of the MI measure.